I heard the guys aren't allowed to touch themselves because its wasted seed but what about girls. Would that be okay?
Rav Nissim Karelitz, based on the Ramban and Ritva in Niddah 13a, holds Chut Shani on Even HaEzer siman 21that there is an issur for a woman to entertain or cause sexual thoughts. The issur is "de'megarei yetzer hara be'nafsheyhu" and not "ve'nishmartah mikol davar rah".
The reason why ve'nishmartah does not apply is because there is no issur of wasting seed for a woman. That being said, practically there would be prohibited (in many circumstances) since it causes forbidden thoughts.
Unlike the prohibition for men that is so severe that not many scenarios can justify it (e.g. as a substitution for adultery), the prohibition for women is far less severe and can be easily justified for a noble purpose.
For ages, the Halachah neglected women sexuality, assuming that women enjoy the closeness and the act itself "no matter what". Times changed, and female sexual satisfaction is an obligatory topic for all of the contemporary Haredi Madrichey Chatanim (and Kalot). I personally spoke to two Madrichim and there was also an interesting documentary on the Israeli TV about Haredi X-shops Rabbinically approved industry.
It is clear today, that the lack of satisfaction on the woman's side can easily sabotage a marriage or put a serious burden on the husband (learning female anatomy and physiology). Therefore, rather secretly and privately, practically all the Rabbis from all Haredi communities, incl the Hassidishers, allow women to enjoy themselves as long as it's intended for Sholom Bays, either with or without the husband and even obligate the husbands to buy toys and devices to enhance it according to every woman's desires.
Enjoying oneself without noble intentions is covered in other answers.
Whilst there is no halachic issur or mention of a woman not being allowed to do this, one of the reasons given is that a man is not permitted to waste his seed and this doesn't apply to a woman. In the same vein this is why she is permitted to use birth control and a man is not. What there is mention of is re tznius that a woman even when in the washroom should be careful about only exposing what is necessary. From this one can deduce that whilst not halachically forbidden, in the spirit of being G-d fearing this practice is not endorsed and not mentioned in seminaries or schools.
Rav moshe says (even Ezer Chelek 1 siman 69) that while it's a violation of BOTH lo tasuru AND vinishmarta mikol davar ra (since it leads to shichvat zera levatala) for a man, for a woman would STILL be in violation of lo tasuru EVEN THOUGH there is no concern for zera.
So Rav Moshe clearly rules that it's ossur.